Method to machine a metal work piece by turning

ABSTRACT

A method to form a surface on a metal work piece includes providing a turning insert having a first cutting edge, a second cutting edge and a convex nose cutting edge connecting the first and second cutting edges, a nose angle formed between the first and second cutting edges being less than or equal to 85°; arranging the second cutting edge such that it forms a back clearance angle of more than 90° in a feed direction; positioning all parts of the turning insert ahead of the nose cutting edge in the feed direction; rotating the metal work piece around a rotational axis in a first direction; and moving the turning insert in a direction parallel to or at an angle less than 45° relative to the rotational axis, such that the surface at least partly is formed by the nose cutting edge.

RELATED APPLICATION DATA

This application claims priority under 35 U.S.C. § 119 to EP PatentApplication No. 15189176.9, filed on Oct. 9, 2015, which the entiretythereof is incorporated herein by reference.

TECHNICAL FIELD

The present disclosure relates to the technical field of metal cutting.More specifically, the field of turning, which is performed by turning ametal work piece using a turning tool in a machine such as aCNC-machine.

The present disclosure refers to a method to form a surface on a metalwork piece, the use of a turning insert in such method, a computerprogram having instructions which when executed by a computer numericalcontrol lathe causes the computer numerical control lathe to performsuch method, a computer readable medium having stored thereon suchcomputer program, and a data stream which is representative of suchcomputer program.

BACKGROUND

In turning of a metal work piece, the metal work piece rotates around acenter axis. The metal work piece is clamped at one end by rotatableclamping means such as one or more chuck or jaws. The end of the workpiece which is clamped can be called a clamping end or a driving end.For stable clamping, the clamping end or the driving end of the metalwork piece may have a larger diameter than the opposite end of the metalwork piece and/or has a larger diameter of a portion of the metal workpiece located between the clamping end and the opposite end.Alternatively, the metal work piece may have a constant diameter beforea machining, i.e. metal cutting, operation.

The turning insert is moved in relation to the metal work piece. Thisrelative movement is called feed. The movement of the turning insert canbe in a direction parallel to the center axis of the metal work piece,this is commonly called longitudinal feed or axial feed. The movement ofturning insert can furthermore be in a direction perpendicular to thecenter axis of the metal work piece, this is commonly called radial feedor facing. Other angles of movement, or feed directions, are alsopossible, this is commonly known as copying or copy-turning.

In copying, the feed has both axial and radial components. During therelative movement of the turning insert, material from the metal workpiece is removed in the form of chips. The chips are may be short and/orhave a shape or direction of movement which prevents chip jamming and/ordo not give a poor surface finish of the machined surface.

Common shapes of turning inserts which can be used for a wide range offeed direction include triangular turning inserts. Such inserts have ina top view, i.e. a rake face towards the viewer, the shape of a trianglewhere all three sides are of equal length and where the nose angle is60°. The corners of the triangle are in the form of nose cutting edges,which typically has a radius of curvature in the range of 0.2-2.0 mm.Examples of such turning inserts are commonly designated TNMG and TCMTaccording to ISO standard, and are commonly made at least partly fromcoated or uncoated cemented carbide or cubic boron nitride (CBN) orceramic or cermet.

Other common shapes of turning inserts have in a top view, i.e. a rakeface towards the viewer, the shape of a rhombus where all four sides areof equal length and where the nose angle of an active nose portion is80°. The active corners are in the form of nose cutting edges, whichtypically has a radius of curvature in the range of 0.2-2.0 mm. Examplesof such turning inserts are commonly designated CNMG according to ISOstandard, and are commonly made at least partly from coated or uncoatedcemented carbide or cubic boron nitride (CBN) or ceramic or cermet.

Both the described triangular and rhombic turning inserts can be usedfor turning two walls forming an external 90° corner in a metal workpiece, where one wall, at a greater distance from the rotational axis ofa metal work piece, is perpendicular to the rotational axis and onecylindrical wall, at a smaller distance from the rotational axis, isparallel to the rotational axis, where the two walls are connected by acircular or curved segment. An external 90° corner in this context is a90° corner formed on or at an external or outer surface of a metal workpiece, such that the cylindrical wall or cylindrical surface is facingaway from the rotational axis. This is in contrast to any corner whichmay be formed on or at an internal or inner surface inside a boreconcentric with the rotational axis.

The circular or curved segment have a cross-section in a plane includingthe rotational axis in the shape of an arc, in the shape of a quarter ofa circle or a quarter of a shape, which is substantially a circle, whichhas the same radius of curvature as the nose cutting edge of the turninginsert. The circular or curved segment alternatively has a greaterradius of curvature than the nose cutting edge of the turning insert.

In EP2572816B1, a turning tool is shown during machining of a workpiece. The turning tool can be used for forming two walls forming anexternal 90° corner, without any reorientation of the turning tool. Thetool includes a holder as well as a turning insert. In this case, thework piece is rotated at the same time as the tool is longitudinally fedparallel to the center axis of the. The setting angle, or enteringangle, is the angle between the direction of the longitudinal feed and amain edge. The setting angle, or entering angle, is 95°. The turninginsert has a rhombic basic shape and comprises two acute-angled cornershaving an angle of 80° and two obtuse-angled ones having an angle of100°. A back clearance angle of 5° is obtained between the turninginsert and the generated surface of the work piece. The generatedsurface of the work piece is substantially cylindrical.

Such a turning method as in EP2572816B1 gives an unsatisfactory toollife, or usage time, for the turning insert.

SUMMARY

To overcome the above disadvantages, the present disclosure is directedto a method to form a surface on a metal work piece including a firstmachining step including the steps of providing a turning insert havinga first cutting edge, a second cutting edge and a convex nose cuttingedge connecting the first and second cutting edges, selecting a noseangle α formed between the first and second cutting edges to be lessthan or equal to 85°; arranging the orientation of the second cuttingedge such that it forms a back clearance angle ψ of more than 90° in afeed direction; positioning all parts of the turning insert ahead of thenose cutting edge in the feed direction; rotating the metal work piecearound a rotational axis A3 in a first direction; and moving the turninginsert in a direction parallel to or at an angle less than 45° relativeto the rotational axis A3, such that the first cutting edge is activeand ahead of the nose cutting edge in the feed direction and such thatthe surface at least partly is formed by the nose cutting edge.

According to the present method, the second cutting edge is not subjectto wear during the first machining step, e.g. an axial turning step, andcan be used in a subsequent second machining step, e.g. an out facingstep i.e. fed perpendicular to and away from the rotational axis of themetal, or metallic, work piece, or in a subsequent turning operation inan substantially opposite or opposite direction relative to the firstdirection.

It is advantageous for the tool life of the turning insert that the wearof the cutting edges is distributed in an equal manner. According to thepresent method, it is possible to use the turning insert in a prior orsubsequent second machining step, e.g. an out facing operation, withoutreorientation, preferably in such a way that insert wear is distributedover a longer cutting edge distance, with little or no overlap for theinsert wear caused by the first machining step and the second machiningstep.

According to the present method, the chip control or chip evacuation isimproved if the feed direction is away from a portion of the work piecewhich has a larger diameter than the diameter of the surface formed,such as for example a wall surface extending in a plane perpendicular tothe rotational axis of the metal work piece.

According to the present method, the entering angle of the first cuttingedge is reduced, resulting in relatively wider and thinner chips, whichthe inventors have found to give reduced wear of the first cutting edge.

The present method is thus related to axial or longitudinal or copyturning, which can be external or internal. The method can be anexternal turning method, i.e. a method where the surface which is formedis facing away from the rotational axis. The surface which is formed, orgenerated, is a rotational symmetrical surface, i.e. a surface which hasan extension along the rotation axis of the metal work piece and wherein a cross sections perpendicular to the rotational axis, each portionof the rotational symmetrical surface is located at a constant distancefrom the rotation axis of the metal work piece, where a constantdistance is a distance which is within 0.10 mm, for example, within 0.05mm.

The rotational symmetrical surface can be in the form of e.g. acylindrical surface or a conical surface or a frustoconical surface or atapered surface. The moving or feed direction of the turning insert isaway from an imaginary plane perpendicular to the rotational axis. Inother words, the moving of the turning insert is with a component of themovement in a direction parallel to the rotational axis of the metalwork piece, e.g. the turning insert moves in a direction parallel to therotational axis, or the turning insert moves in a direction at an angle,for example, an angle less than 15°, relative to the rotational axis.

In the first example, the rotational symmetrical surface is acylindrical surface which is symmetrical around the rotational axis. Inthe second example, the rotational symmetrical surface is a conicalsurface, or a frustoconical surface, or a tapered surface, which issymmetrical around the rotational axis. The rational symmetrical surfacegenerated or formed at least partly by the nose cutting edge has a wavyshape with small peaks and valleys, and the wavy shape is influenced atleast partly by the curvature of the nose radius and the feed rate. Thewave height is less than 0.10 mm, for example, less than 0.05 mm.

To form, or generate, a rotational symmetrical surface in this meaningis by metal cutting, where chips from the metal work piece are removedby at least one cutting edge. The final shape of the rotationalsymmetrical surface is formed solely or at least to the greatest extentor at least partly by the nose cutting edge. This is because the nosecutting edge is the part of the turning insert which is located at ashorter distance from the rotation axis of the metal work piece than allother parts of the turning insert.

More specifically, during the first machining step, one first point ofthe nose cutting edge is the part of the turning insert which is locatedclosest to the rotational axis of the metal work piece. One secondpoint, or trailing point, of the nose cutting edge, which is behind thefirst point in the feed direction, is the part of the turning insertwhich is located most rearward in the feed direction or in the directionof insert movement. This first point of the nose cutting edge is locatedon the same side of the bisector as the first cutting edge, where thebisector is a line which is between the first and second cutting edgesat equal distance from the first and second cutting edges.

The second point of the nose cutting edge is located on the same side ofthe bisector as the second cutting edge. The first cutting edge and thesecond cutting edge are located on opposite sides of the convex nosecutting edge. The first, second and nose cutting edges are formed atborders of a top surface of the turning insert, which top surfacecomprises a rake face.

The expression “positioning all parts of the turning insert ahead of thenose cutting edge in the feed direction” thus can alternatively beformulated as “positioning all parts of a top surface of the turninginsert ahead of a trailing portion of the nose cutting edge in the feeddirection.”

The nose angel of less than or equal to 85° gives a similar advantage asthat of a 90° corner, i.e. two wall surfaces being perpendicular to eachother that can be machined with one nose portion of the turning insert,without any reorientation of the turning insert. Alternatively, a noseangle less than or equal to 85° is equal to a nose cutting edge havingthe shape of a circular arc of an angle of less than or equal to 85°.

The nose cutting edge may have a shape of a circular arc, or may have ashape that deviates slightly from a perfect circular arc. The nosecutting edge can have a radius of curvature of 0.2-2.0 mm.

The first and second cutting edges can be straight in a top view.Alternatively, the first and second cutting edges can be slightly convexor concave, with a radius of curvature that is more than two timesgreater, for example, more than ten times greater, than the radius ofcurvature of the convex nose cutting edge.

The moving of the turning insert is commonly known as feed. If the feedis parallel to the rotational axis of the metal work piece, it is calledaxial feed or longitudinal feed. The first cutting edge is ahead of thenose cutting edge in the feed direction. In other words, the firstcutting edge forms, or is active at, an entering angle less than 90° andmore than 1°, less than 45° and more than 3°, and less than 45° and morethan 10°. In other words, the first cutting edge is a leading edge. Theentering angle is the angle between the feed direction and the activecutting edge, which in this case is first cutting edge.

The second cutting edge forms a back clearance angle ψ of more than 90°,for example, more than 100°. In other words, the second cutting edge isa trailing edge. The angle between the feed direction, i.e. thedirection of movement of the turning insert, and the second cutting edgeis less than 90°, for example, less than 80°. In turning, at least inturning where a first cutting edge and a second cutting edge is locatedin a plane comprising the rotation axis, the entering angle plus thenose angle (the angle between the first and second cutting edgesadjacent on opposite sides of the nose cutting edge) plus the backclearance angle ψ equals 180°.

In FIG. 2 where the feed is parallel to the rotation axis, the backclearance angle is 90° plus κ2. Alternative formulations of the backclearance angle ψ includes end cutting edge angle, free cutting angle,and plan trail clearance angle. The rotating and moving are motionswhich are relative, which means that although it is preferred that themetal work piece rotates and that the turning insert moves in an axialdirection, it is possible in e.g. bar peeling machines that the turninginsert rotates around a non-rotating metal work piece, and that themetal work piece moves in an axial direction.

The turning insert can be mounted in a tool body. The tool body is turnmounted in a turning lathe or a CNC-machine.

The feed rate can be less than or equal to the radius of curvature ofthe nose cutting edge, if the nose cutting edge has a constant radius ofcurvature. This is to generate an acceptable surface finish. Forexample, for a turning insert having a nose cutting edge with a radiusof curvature of 0.8 mm, the feed rate being less than or equal to 0.8 mmper revolution. For turning inserts having a nose cutting edge whichdeviates slightly from a circular arc, such as so called wiper radius orwiper insert, the feed rate can be slightly higher while stillgenerating an acceptable surface finish. The formed or generated surfacehas an extension which corresponds to the feed direction.

According to an embodiment, the first machining step further includesthe steps of clamping the metal work piece at a first end, setting thenose cutting edge a shorter distance to the first end than all otherparts of the turning insert and moving the turning insert in a directionaway from the first end.

According to the present method, chip jamming is further improved,because the moving of the turning insert, i.e. the feed direction, istowards an un-clamped or free end of the metal work piece.

The first end of the metal work piece is a clamping end or driving end.Thus, the clamping means, e.g. chuck or clamping jaws or tail stock,which holds the metal work piece, are controlled and driven by a motorhold the metal work piece in the first end. The headstock end of themachine is located at the first end of the metal work piece. Thediameter of the first end of the metal work piece can be greater thanthe diameter of the surface.

According to an embodiment, the first machining step further includesthe step of arranging the first cutting edge such that the first cuttingedge cuts metal chips from the metal work piece at an entering angle κ1of 10-45°.

The first cutting edge is thus active at an entering angle κ1 of 10-45°,for example, 20-40°. A lower entering angle gives too wide chipsresulting in reduced chip control, and the risk of vibration wouldincrease. A higher entering angle gives increased insert wear of thefirst cutting edge. Accordingly, the nose angle, i.e. the angle whichthe first and second cutting edges form relative to each other in a topview, is 25-50°. A top view is where a top surface, i.e. a rake face, ofthe turning insert is facing the viewer and is perpendicular to the viewdirection. The cutting depth can be 0.05-5.0 mm.

According to an embodiment, the first machining step further includesthe step of providing that the turning insert comprises a third convexcutting edge adjacent to the first cutting edge and a fourth cuttingedge adjacent to the third cutting edge, the method further includingthe step of arranging the forth cutting edge such that the fourthcutting edge cuts metal chips from the metal work piece at an enteringangle κ1 of 10-45°.

According to the present method, the tool life of the turning insert isfurther increased, i.e. the wear is further reduced, especially atrelatively larger depths of cut, such as e.g. depth of cut greater than1.0 mm.

The nose angel α, i.e. the angle between the first and second cuttingedges, can be 70-85°. Thus, the wear of the nose cutting edge is furtherreduced.

According to an embodiment, the first machining step further includesthe step of entering the turning insert into the metal work piece at anangle relative to the rotation axis A3 which is less than 90°, and whichangle is greater than the angle formed between the feed direction of theturning insert and the rotational axis A3. Accordingly, the wear,especially the wear at the nose cutting edge, of the turning insert 1 isfurther reduced. The turning insert is thus entering the metal workpiece, i.e. going into the cut, gradually.

According to an embodiment, the first machining step further includesthe step of entering the turning insert into the metal work piece suchthat the nose cutting edge moves along an arc of a circle. Thus, thewear, especially the wear at the nose cutting edge, of the turninginsert is further reduced. When the turning insert enters the metal workpiece, i.e goes into the cut, the nose cutting edge moves along an arcof a circle.

According to an embodiment, the first machining step further includesthe step of entering the turning insert into the metal work piece suchthat the chip thickness during entry is constant or substantiallyconstant. Accordingly, the insert wear is further reduced.

Chip thickness is defined as feed rate multiplied by sinus for theentering angle. Thus, by choosing and/or varying the feed rate and themovement and/or direction of the turning insert during entry, the chipthickness can be constant or substantially constant. The feed rateduring entry can be less or equal than 0.50 mm/revolution. The chipthickness during entry can be less than or equal to the chip thicknessduring subsequent cutting or machining.

According to an embodiment, the surface is an external cylindricalsurface, and in the moving of the turning insert is in a directionparallel to the rotational axis A3.

An external cylindrical surface is a surface having an extension alongand at a constant or substantially constant distance from the rotationalaxis. The moving of the turning insert is the feed direction.

According to an embodiment, the turning insert has a top surface and anopposite bottom surface. A reference plane RP is located parallel to andbetween the top surface and the bottom surface. The present methodfurther includes the step of arranging the first cutting edge such thatthe distance from the first cutting edge to the reference plane RPdecreases as the distance from the nose cutting edge. In other words,this distance is decreasing as the distance from the nose cutting edgeincreases.

According to the present method, the chip breaking and/or chip controland/or tool life, i.e. insert wear, is improved, in axial turning awayfrom the clamping end of the metal work piece.

The top surface can be a rake face. The bottom surface acts as a seatingsurface. The reference plane is parallel to a plane in which the nosecutting edges are located. The distance from different points of thefirst cutting edge to the reference plane varies in such a way that thatthis distance is decreasing at an increasing distance from the nosecutting edge. In other words, the distance from the first cutting edgeto the reference plane is decreasing away from the nose cutting edge.

Alternatively formulated, a distance from the reference plane to a firstportion of the first cutting edge is greater than a distance from thereference plane to a second portion of the first cutting edge, where thefirst portion of the first cutting edge is located between the nosecutting edge and the second portion of the first cutting edge. Forexample, a first point of the first cutting edge, adjacent to the nosecutting edge, is located a greater distance from the reference planethan a distance from a second point of the first cutting edge, locatedat a greater distance from the nose cutting edge than the first point ofthe first cutting edge, to the reference plane. The first cutting edgeis sloping towards the bottom surface and the reference plane away fromthe nose cutting edge in a side view.

According to an embodiment the turning insert includes a top surface, anopposite bottom surface, and a reference plane RP is located parallel toand between the top surface and the bottom surface. The method furtherincludes the step of arranging the fourth cutting edge such that thedistance from the fourth cutting edge to the reference plane RPdecreases at increasing distance from the nose cutting edge. By such amethod the chip breaking and/or chip control and/or tool life, i.e.insert wear, is improved, in axial turning away from the clamping end ofthe metal work piece.

The top surface provides a rake face. The bottom surface provides aseating surface. The reference plane is parallel to a plane in which thenose cutting edges are located. The distance from the fourth cuttingedge to the reference plane varies in such a way that that this distanceis decreasing at increasing distance from the nose cutting edge. Inother words, the distance from the fourth cutting edge to the referenceplane is decreasing away from the nose cutting edge. Alternativelyformulated, a distance from the reference plane to a first portion ofthe fourth cutting edge is greater than a distance from the referenceplane to a second portion of the fourth cutting edge, where the firstportion of the fourth cutting edge is located between the nose cuttingedge and the second portion of the fourth cutting edge. For example, afirst point of the fourth cutting edge, closer to the nose cutting edge,is located a greater distance from the reference plane than a distancefrom a second point of the fourth cutting edge, located at a greaterdistance from the nose cutting edge than the first point of the fourthcutting edge, to the reference plane. The fourth cutting edge slopestowards the bottom surface and the reference plane away from the nosecutting edge in a side view.

According to an embodiment, the method further includes the step ofsetting the back clearance angle constant in relation to the feeddirection during the formation of the surface. In other words, in thecase of a constant feed direction when forming the surface, the backclearance angle is constant when forming the surface. Thus, during theformation of the surface the turning insert do not rotate around anyaxis.

According to an embodiment, the method further includes the step ofproviding a turning tool having the turning insert and a tool body,wherein the method includes the further step of positioning all parts ofthe tool body ahead of the nose cutting edge in the feed direction. Inother words, the turning tool is ahead of the nose cutting edge in thefeed direction. By such a method, the possibility of out facing, orfeeding in a direction perpendicular to and away from the rotationalaxis of the metal work piece, is further improved.

According to an embodiment, the method further includes the step ofproviding a turning tool including the turning insert and a tool body,the tool body having a front end and a rear end, a main extension alonga longitudinal axis extending from the front end to the rear end, aninsert seat formed in the front end in which the turning insert ismountable. The method further includes the step of setting thelongitudinal axis of the tool body at an angle greater than zero butless than or equal to 90° relative to the rotational axis of the metalwork piece.

According to the present method, the risk of vibrations is reduced,compared to if the longitudinal axis of the tool body were parallel tothe rotational axis of the metal work piece, at least in the case wherethe feed direction is parallel to the rotational axis of the metal workpiece. According to the present method, the possibility to machine deepcavities or deep pockets are improved, because the risk of the tool bodyinterfering the metal work piece is reduced. The setting of thelongitudinal axis of the tool body is perpendicular, i.e. 90°, to therotational axis of the metal work piece. The longitudinal axis of thetool body can be at a constant angle relative to the longitudinal axisof the tool body.

According to an embodiment, the method includes a second machining stepof moving the turning insert in a direction away from the rotation axisA3 such that the second cutting edge cuts chips from the metal workpiece, and such that a surface perpendicular to the rotational axis A3of the metal work piece is formed.

According to the present method, two surfaces, which together form acorner, such as a 90° corner, can be formed with the same turning insertwithout reorientation of the turning insert, with reduced wear of theturning insert. More specifically, the insert wear is distributed in amore even manner, giving prolonged tool life.

The direction of the movement of the turning insert is away from therotational axis of the metal work piece, i.e., in a directionperpendicular to the rotational axis, or at an angle which deviates upto 20° from a perpendicular direction to the rotational axis. Thedirection of rotation of the metal work piece around the rotational axisis the same direction for the first and second machining steps. Thesecond machining step can be made either prior to or after the firstmachining step. The orientation of the turning insert can be constantduring the first and second machining steps. Constant orientation meansthat the angles which parts of the turning insert, such as the firstcutting edge, forms in relation to or relative to the rotational axis ofthe metal work piece is constant or has the same value at both the firstand second machining steps.

According to an embodiment, the method includes the step of in asequence alternating the first and second machining steps, such that acorner having two surfaces is formed. According to the present method,the insert wear is further reduced. By such a method, the risk for chipjamming is further reduced, because the cutting time for each cut isreduced.

According to an embodiment, the method includes the step of in asequence alternating the first and second machining steps, such that anexternal 90° corner having two wall surfaces is formed, wherein one wallsurface is an outer cylindrical surface and in that one wall surface isperpendicular to the rotational axis A3 of the metal work piece.

According to the present method, an external 90° corner can be formedwith less risk of chip jamming, because the feed direction or themovement of the turning insert is not towards the wall surface which isperpendicular to the rotational axis of the metal work piece. Accordingto the present, an external 90° corner can be formed with reduced insertwear.

The direction of movement of the turning insert during the firstmachining step is parallel to the rotational axis of the metal workpiece. The direction of movement of the turning insert during the secondmachining step is perpendicular to and away from the rotational axis ofthe metal work piece. The direction of movement in this sense is duringthe major part of each machining step.

The entry or start or going into the cut part of each machining step isat least partly in a different direction than the major part. The entryor start or going into the cut part is thus a minor part of eachmachining step, in the sense that the volume of removed metal is lessthan 20% than the metal removed from the major part. The surface formedwhich is perpendicular to the rotational axis is a flat or substantiallyflat surface, i.e. the surface is located in a single plane.Substantially flat in this sense is a wavy surface, where the wave depthor wave height is less than 0.1 mm, for example, less than 0.05 mm.

The external 90° corner includes two wall surfaces, which are connectedby a curved or arc-shaped surface. The radius of curvature of the curvedor arc-shaped surface is equal to or greater than the radius ofcurvature of the nose cutting edge of the turning insert. The curved orarc-shaped surface has a surface area which can be less than 50%, forexample, less than 10%, of the surface area of each of the wallsurfaces.

According to an embodiment, the method includes a third machining step,including the steps of rotating the metal work piece around the rotationaxis A3 in a second direction, in that the second direction of rotationis opposite to the first direction of rotation, and moving the turninginsert in a direction towards the rotation axis A3 such that the secondcutting edge cuts chips from the metal work piece.

Thus, during the third machining step, at least the second cutting edgeof the turning insert is located on an opposite side or a substantiallyopposite side of the rotational axis, compared to the location of atleast the first cutting edge of the turning insert during the firstmachining step. The third machining step can be performed prior to orafter the first machining step. The third machining step can beperformed prior to or after the second machining step. The thirdmachining step can include a moving of the turning insert perpendicularto the rotational axis of the metal work piece.

According to an embodiment, the method includes the step of providing aturning tool comprising the turning insert and a tool body, the toolbody having a front end and a rear end, a main extension along alongitudinal axis A2 extending from the front end to the rear end, aninsert seat formed in the front end in which the turning insert ismountable such that a bisector extending equidistantly from the firstand second cutting edges forms an angle θ of 35-55° in relation to thelongitudinal axis A2 of the tool body.

According to an embodiment, the method includes the step of arrangingthe first cutting edge a shorter distance from the longitudinal axis A2of the tool body than the distance from the second cutting edge to thelongitudinal axis A2 of the tool body.

According to another aspect of the present disclosure, at least theabove mentioned primary objective is achieved by means of the use of aturning insert in the method as initially defined.

According to a third aspect of the present disclosure, at least theabove mentioned primary objective is achieved by means of a computerprogram having instructions, which when executed by a computer numericalcontrol lathe, cause the computer numerical control lathe to perform themethod as initially defined.

The method and methods described herein may be embodied by a computerprogram or a plurality of computer programs, which may exist in avariety of forms both active and inactive in a single computer system oracross multiple computer systems. For example, they may exist assoftware program(s) of program instructions in source code, executablecode or other formats for performing some of the steps. Any of the abovemay be embodied on a computer readable medium, which include storagedevices and signals, in compressed or uncompressed form. The termcomputer numerical control (CNC) lathe refers to any machine which canbe used for turning a metal work piece, and where the motion of themachine, such as tool path, depth of cut, feed rate, cutting speed andrevolutions per time unit, is or can be controlled by a computer.

According to a fourth aspect of the present disclosure, at least theabove mentioned primary objective is achieved by means of a computerreadable medium having stored thereon a computer program havinginstructions which when executed by a computer numerical control lathecause the computer numerical control lathe to perform the method asinitially defined.

As used herein, a computer readable medium or storage medium can be anymeans that contain, store, communicate, propagate or transport theprogram for use by or in connection with the instruction executionsystem, apparatus, or device. The computer readable medium can be, forexample but not limited to, an electronic, magnetic, optic,electromagnetic, infrared, or semiconductor system, device, orpropagation medium. More examples (a non-exhaustive list) of thecomputer readable medium can include the following: an electricalconnection having one or more wires, a portable computer diskette, arandom access memory (RAM), a read only memory (ROM), an erasableprogrammable read only memory (EPROM or Flash memory), an optical fiber,and a portable compact disc read only memory (CDROM).

According to a fifth aspect of the present disclosure, at least theabove mentioned primary objective is achieved by means of a data streamwhich is representative of a computer program having instructions whichwhen executed by a computer numerical control lathe cause the computernumerical control lathe to perform the method as initially defined.

The foregoing summary, as well as the following detailed description ofthe embodiments, will be better understood when read in conjunction withthe appended drawings. It should be understood that the embodimentsdepicted are not limited to the precise arrangements andinstrumentalities shown.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic view showing conventional turning of a cylindricalsurface with a conventional turning insert.

FIG. 2 is a schematic view illustrating turning of a cylindrical surfaceby a first turning insert.

FIG. 2a is a schematic view showing turning of a cylindrical surface bya third turning insert.

FIG. 3 is a schematic view illustrating turning, including axial turningand out-facing, of a metal work piece with the first turning insert.

FIG. 3a is a schematic view showing turning, including axial turning andout-facing, of a metal work piece by a third turning insert.

FIG. 4 is a schematic view illustrating turning, including out-facing,of a metal work piece with the first turning insert.

FIG. 5 is a top view of a top surface of a nose portion of the firstturning insert.

FIGS. 6-8 are detailed cross-sectional views taken along the linesVI-VI, VII-VII and VIII-VIII, respectively, in FIG. 5.

FIG. 9 is a side view of the nose portion in FIG. 5.

FIG. 10 is a schematic view showing a turning method according to anembodiment forming a surface using a conventional turning insert.

FIG. 11 is a schematic top view of a nose portion of a conventionalturning insert, showing wear from conventional turning.

FIG. 12 is a schematic top view of a nose portion, showing wear fromturning in FIG. 13.

FIG. 13 is a schematic view illustrating turning of a 90° corner by thefirst turning insert.

FIG. 14a is a perspective view showing a second turning insert.

FIG. 14b is a front view of the turning insert in FIG. 14 a.

FIG. 14c is a side of the turning insert in FIG. 14 a.

FIG. 14d is a top view of the turning insert in FIG. 14 a.

FIG. 14e is a perspective view showing the turning insert in FIG. 14apositioned in a partial tool body.

FIG. 14f is an exploded view showing the turning insert and tool body inFIG. 14 e.

FIG. 15a is a perspective view showing a third turning insert.

FIG. 15b is a front view of the turning insert in FIG. 15 a.

FIG. 15c is a side of the turning insert in FIG. 15 a.

FIG. 15d is a top view of the turning insert in FIG. 15 a.

FIG. 15e is a top view of the turning insert in FIG. 15a and a toolbody.

FIG. 15f is a top view of the tool body in FIG. 15 e.

FIG. 16a is a perspective view showing the first turning insert.

FIG. 16b is a front view of the turning insert in FIG. 16 a.

FIG. 16c is a side view of the turning insert in FIG. 16 a.

FIG. 16d is a top view of the turning insert in FIG. 16 a.

FIG. 17a is a perspective view showing the turning insert In FIG. 16aand a tool body.

FIG. 17b is a perspective view showing the bottom surface of the turninginsert in FIG. 16a

FIG. 17c is a further perspective view showing the bottom surface of theturning insert in FIG. 16a

FIG. 17d is a perspective view showing the turning insert in FIG. 15aseated in a tool body.

FIG. 17e is a perspective view showing the turning insert in FIG. 15aand a tool body.

FIG. 17f is a top view showing the turning insert and the tool body inFIG. 17 d.

FIG. 18a s a perspective view showing a fourth turning insert.

FIG. 18b is a top view of the turning insert in FIG. 18 a.

FIG. 18c is a bottom view of the turning insert in FIG. 18 a.

FIG. 18d is a side view of the turning insert in FIG. 18 a.

FIG. 18e is a front top view of the turning insert in FIG. 18 a.

FIG. 19a is a perspective view showing a fifth turning insert.

FIG. 19b is a top view of the turning insert in FIG. 19 a.

FIG. 19c is a bottom view of the turning insert in FIG. 19 a.

FIG. 19d is a side view of the turning insert in FIG. 19 a.

FIG. 19e is a front top view of the turning insert in FIG. 19 a.

FIG. 20a is a perspective view showing a sixth turning insert.

FIG. 20b is a top view of the turning insert in FIG. 20 a.

FIG. 20c is a bottom view of the turning insert in FIG. 20 a.

FIG. 20d is a side view of the turning insert in FIG. 20 a.

FIG. 20e is a front top view of the turning insert in FIG. 20 a.

FIG. 21a is a perspective view showing a seventh turning insert.

FIG. 21b is a top view of the turning insert in FIG. 21 a.

FIG. 21c is a bottom view of the turning insert in FIG. 21 a.

FIG. 21d is a side view of the turning insert in FIG. 21 a.

FIG. 21e is a front top view of the turning insert in FIG. 21 a.

FIG. 22a is a perspective view showing an eighth turning insert.

FIG. 22b is a top view of the turning insert in FIG. 22 a.

FIG. 22c is a bottom view of the turning insert in FIG. 22 a.

FIG. 22d is a side view of the turning insert in FIG. 22 a.

FIG. 22e is a front top view of the turning insert in FIG. 22 a.

All turning insert figures except FIGS. 1 and 10 have been drawn toscale.

DETAILED DESCRIPTION

Reference is made to FIG. 1, which show a conventional metal cuttingoperation by turning using a conventional turning insert 1. A metal workpiece 50 is clamped by clamping jaws 52, which are connected to amachine comprising a motor (not shown), such as a CNC-machine or aturning lathe. The clamping jaws press against an external surface at afirst end 54, or clamping end, of the metal work piece 50.

An opposite second end 55 of the metal work piece 50 is a free end. Themetal work piece 50 rotates around a rotational axis A3. The turninginsert 1 is securely and removably clamped in an insert seat or a pocketin a tool body 2. The tool body 2 has a longitudinal axis A2, extendingfrom a rear end to a front end, in which the insert seat or pocket islocated. The tool body 2 and the turning insert 1 together form aturning tool 3.

The turning tool 3 is moved in relation to the metal work piece 50,commonly designated feed. In FIG. 1, the feed is axial, also calledlongitudinal feed, i.e. the direction of the feed is parallel to therotational axis A3. In this way, a cylindrical surface 53 is formed.

The turning insert 1 has an active nose with a nose angle α which is80°, defined as the angle between the main cutting edge and thesecondary cutting edge. As the turning insert 1 reaches closer to thewall surface which is perpendicular to the rotational axis A3, chipcontrol is poor because there is not much space for the chips to get outfrom the cutting zone. There is also risk that chips hits or damages themachined surface.

The main cutting edge is behind the nose cutting edge. In other words,the entering angle for the main cutting edge is over 90°, in FIG. 1around 95°. The entering angle is defined as the angle between thecutting edge and the feed direction. In the turning method shown in FIG.1, the back clearance angle is around 5°. The back clearance angle ψ isdefined as the angle between the secondary cutting edge, which is atrailing edge, and a direction which is opposite, i.e. 180° in relation,to the feed direction.

Reference is made to FIG. 2, which show a turning operation, using aturning tool including a first turning insert. As in FIG. 1, a metalwork piece is clamped by clamping jaws (not shown), which are pressedagainst an external surface at or adjacent to a first end 54 of themetal work piece. An opposite second end 55 of the metal work piece is afree end. The metal work piece rotates around a rotational axis A3. Theturning insert, seen in top view, is securely and removably clamped inan insert seat or a pocket in tool body 2 by means of a screw 6. Thetool body 2 has a longitudinal axis A2, extending between a rear end anda front end 44, in which the insert seat or pocket is located.

In FIG. 2, the feed is, to a greatest extent, axial, also calledlongitudinal feed, i.e. the direction of the feed is parallel to therotational axis A3. In this way, an external cylindrical surface 53 isformed. At the entry of each cut, or immediately prior to the axialfeed, the feed has a radial component, in such a way that the turninginsert move along an arc of a circle.

The turning insert includes an active nose portion 15, including anactive nose cutting edge 10. The active nose portion 15 further includesan active first cutting edge, which during axial turning parallel to therotational axis A3 has an entering angle κ1 which is chosen to be in therange of 10-45°, for example, 20-40°.

The first cutting edge, which is the main cutting edge in the operation,is ahead of the nose cutting edge 10 in the axial feed direction. Inother words, the first cutting edge is a leading edge. A second cuttingedge, formed on or at the active nose portion 15, is a secondary cuttingedge or a trailing edge. If the feed direction would be radial, in sucha way that the feed direction would be perpendicular to and away fromthe rotational axis A3, the second cutting edge would be active at anentering angle κ2.

A bisector 7 is defined by the first and second cutting edges. In otherwords, the bisector is formed between the first and second cuttingedges. The first and second cutting edges converge at a point outsidethe turning insert. The bisector of the active nose portion 15 forms anangle θ of 40-50°, relative to the longitudinal axis A2.

The turning insert includes two inactive nose portions, comprising twoinactive nose cutting edges 10′, 10″. In the axial turning operation,all parts of the turning insert are ahead of the active nose cuttingedge 10 in the feed direction. In the axial turning operation, chips canbe directed away from the metal work piece in a trouble-free manner.

In the machining step the turning insert 1 enters into the metal workpiece 50 such that the nose cutting edge 10 moves along an arc of acircle. The turning insert 1 enters into the metal work piece 50, orgoes into cut, such that the chip thickness during entry is constant orsubstantially constant. At the entry, the depth of cut is increased fromzero depth of cut. Such preferred entry reduces the insert wear,especially the wear at the nose cutting edge 10. Chip thickness isdefined as feed rate multiplied by entering angle. Thus, by choosingand/or varying the feed rate and the movement and/or direction of theturning insert during entry, the chip thickness can be constant orsubstantially constant. The feed rate during entry can be less than orequal than 0.50 mm/revolution. The chip thickness during entry can beless than or equal to the chip thickness during subsequent cutting ormachining.

The cylindrical surface 53, or rational symmetrical surface, generatedor formed at least partly by the nose cutting edge in FIGS. 1 and 2, hasa wavy shape with small peaks and valleys, and the wavy shape isinfluenced at least partly by the curvature of the nose radius and thefeed rate. The wave height is less than 0.10 mm, for example, less than0.05 mm. A thread profile is not a cylindrical surface 53 in this sense.

In FIGS. 3 and 4, the turning insert and tool body in FIG. 2 can be seenin alternative machining operations, showing the versatile applicationarea of the turning tool, especially with regard to feed direction. FIG.3 shows a machining sequence in six steps. Step 1 is a undercuttingoperation. Step 2 is axial turning away from the first end 54 orclamping end of the metal work piece. Step 3 is a profiling operation inthe form of a feed which has both an axial and a radial component,generating a conical or frustoconical, i.e. tapered, surface. Step 4 isan operation similar to operation 2. Step 5 is an out-facing operationgeneration a flat surface located in a plane perpendicular to therotational axis A3 of the metal work piece. Step 6 is an out-facingoperation at the second end 55 or free end of the metal work piece.

FIG. 4 shows two machining steps, step 1 and step 2. In step 1, theradial feed is perpendicular to and towards the rotational axis A3. In2, the radial feed is perpendicular to and away from the rotational axisA3, wherein a flat surface 56 perpendicular to the rotational axis A3 isgenerated. In both cases, the second cutting edge is active at anentering angle κ2 which is in the range of 10-45°, for example, 20-40°.The direction of rotational of the metal work piece around therotational axis A3 is in opposite directions for step 1 and 2. In step2, the direction of rotation is the same as in FIG. 1-3.

FIG. 5 shows a top view of a nose portion 15 of the first turninginsert, having a first 11 and a second 12 cutting edge connected by aconvex nose cutting edge 10. The first 11 and second 12 cutting edges onor at the same nose portion 15 form a nose angle α of 25-50° relative toeach other, and the first 11 and second 12 cutting edges converge at apoint (not shown) outside of the turning insert. A bisector 7 is locatedbetween, and at equal distances from, the first 11 and second 12 cuttingedges. The bisector 7 intersects the nose cutting edge 10 at the centerthereof.

A protrusion 30 is formed in the top surface of the turning insert,which protrusion has the major extension thereof along the bisector. Theprotrusion includes a first chip breaker wall 34 facing towards thefirst cutting edge, and a second chip breaker wall facing the secondcutting edge. The distance, measured in a direction perpendicular to thefirst cutting edge 11, and in a plane parallel to a reference plane RP,from the first cutting edge 11 to the first chip breaker wall 34 isincreasing away from the nose cutting edge 10. This gives improved chipcontrol especially in a turning operation as in FIG. 2. The protrusion30, and thus the first chip breaker wall 34, has a shorter extensionthan the first cutting edge 11.

FIG. 9 shows a side view of the nose portion in FIG. 5. A bottom surface9 is located opposite a top surface. The reference plane RP is locatedbetween and at equidistant length from the top and bottom 9 surfaces.Although the top and bottom surfaces are not flat, the reference planeRP can be positioned such that it is parallel to a plane intersectingthe three nose cutting edges. A side surface 13 connects the top surfaceand the bottom surface 9. The side surface 13 includes a first clearancesurface 21 adjacent to the first cutting edge 11, a third clearancesurface 23 adjacent to the bottom surface 9, and a second clearancesurface 22 located between the first clearance surface 21 and the thirdclearance surface 23.

The distance from the first cutting edge 11 to lower border line of thefirst clearance surface 21, i.e. the border line of the first clearancesurface 21 located closest to the bottom surface 9, is decreasing awayfrom the nose cutting edge. The height, in a direction perpendicular tothe reference plane RP, of the first clearance surface 21 is less thanthe height of the second clearance surface 22, in order to furtherincrease the strength of the first cutting edge 11. The height of thefirst clearance surface 21 is at least 0.3 mm in order to compensate forflank wear of the first cutting edge 11.

The first cutting edge 11 slopes towards the bottom surface 9 and thereference plane RP slopes away from the nose cutting edge 10. Thedistance from the first cutting edge 11 to the reference plane RP variesin such a way that that this distance is decreasing at an increasingdistance from the nose cutting edge 10, at least for a portion of thefirst cutting edge 11. A distance from the reference plane RP to a firstportion of the first cutting edge 11, located adjacent to the nosecutting edge 10, is greater than a distance from the reference plane RPto a second portion of the first cutting edge 11, located further awayfrom the nose cutting edge 10. By such orientation of the first cuttingedge 11, the chip control is improved in axial turning away from theclamping end, as e.g. in an operation as seen in FIG. 2. A distance D1is measured in a direction perpendicular to the reference plane RP,representing the distance between the top surface of the protrusion 30and the lowest point of the first cutting edge 11. D1 is 0.28-0.35 mm.By this, the chip breaking and/or chip control is further improved, inan operation as seen in FIG. 2.

FIGS. 6-8 show cross-sectional views taken along the lines VI-VI,VII-VII and VIII-VIII, respectively, in FIG. 5. The sections areperpendicular to the first cutting edge 11 in planes perpendicular tothe reference plane RP. In FIGS. 6-8, the angles which the first, secondand third clearance surfaces 21, 22, 23 form in relation to a planeparallel to the reference plane RP and intersecting the bottom surface 9are designated γ, σ and ϵ, respectively. Angle σ is greater than angleϵ. By this, out-facing can be made from a smaller work piece diameterwith a reduced decrease in insert strength. Greater clearance angles arenecessary at smaller diameters, but a great and constant clearance anglewould give a reduced strength of the insert.

The second clearance surface 22 has the purpose of increasing thestrength of the insert. The third clearance surface 23 is adjacent tothe bottom surface. Angle γ is greater than angle ϵ. Angle σ is greaterthan γ. The third clearance surface 23 is convex or substantiallyconvex, seen in cross section as in FIGS. 6-8, in order to furtherimprove the lower diameter range, i.e. the minimum diameter where theturning insert can function in an out facing operation, while minimizingthe reduction of insert strength.

The configuration of second cutting edge 12, and the side surface 13adjacent to the second cutting edge 12 are in accordance with theconfiguration of the first cutting edge 11, and the side surface 13adjacent to the first cutting edge 11, which has been described inrelation to FIGS. 5-8 above.

FIG. 10 shows a method to form a surface 53 on a metal work piececomprising a first machining step. A known turning insert 1 is provided.The turning insert 1 includes an active nose portion 15. The active noseportion 15 includes a first cutting edge 11, a second cutting edge 12and a convex nose cutting edge 10 connecting the first 11 and second 12cutting edges. A nose angle α formed between the first 11 and second 12cutting edges is less than or equal to 85°. The nose angle α is at least25°. In FIG. 10, the nose angle α is 80°. The second cutting edge 12forms a back clearance angle ψ of more than 90° in a feed direction 99.If a subsequent or prior machining step is an out-facing operation, theback clearance angle ψ is at least 100°. For example, the back clearanceangle ψ is less than 120°. The back clearance angle ψ is constant inrelation to the feed direction 99 during the formation of the surface53.

All parts of the turning insert 1 are ahead of the active or surfacegenerating nose cutting edge 10 in the feed direction 99. Alternativelyformulated, all parts of a top surface of the turning insert are aheadof a trailing portion of the nose cutting edge in the feed direction.

One first point of the nose cutting edge 10 is the part of the turninginsert 1 that is located closest to the rotational axis of the metalwork piece. One second point, or trailing point, of the nose cuttingedge 10, which is behind the first point in the feed direction 99, isthe part of the turning insert 1 that is located most rearward in thefeed direction 99 or in the direction of insert movement. The firstpoint of the nose cutting edge 10 is located on the same side of abisector as the first cutting edge 11, wherein the bisector is a linewhich is between the first and second cutting edges 11, 12 at equaldistance from the first and second cutting edges 11, 12. The secondpoint of the nose cutting edge 10 is located on the same side of thebisector as the second cutting edge 12. The first cutting edge 11 andthe second cutting edge 12 are located on opposite sides of the convexnose cutting edge 10.

The first, second and nose cutting edges 11, 12, 10 are formed atborders of a top surface of the turning insert 1, which top surfaceincludes a rake face. The expression “positioning all parts of theturning insert ahead of the nose cutting edge in the feed direction”thus can alternatively be formulated as “positioning all parts of a topsurface of the turning insert ahead of a trailing portion of the nosecutting edge in the feed direction.”

All parts of the turning tool 3, including the turning insert 1 and atool body 2, are ahead of the active or surface generating nose cuttingedge 10 in the feed direction. Thus, all parts of the tool body 2 areahead of the nose cutting edge 10 in the feed direction 99. The turningtool 3 is clamped or connected to a turning lathe, such as a CNC-machineor CNC-lathe (not shown). A metal work piece, on which the surface 53 isformed, rotates around a rotational axis (not shown).

The tool body 2 includes a front end and a rear end, a main extensionalong a longitudinal axis A2 extending from the front end to the rearend, and an insert seat formed in the front end in which the turninginsert 1 is mounted. The longitudinal axis A2 of the tool body 2 isperpendicular to the rotational axis of the metal work piece.

The turning insert 1 moves in a direction, defined by the feed direction99, which is parallel to or at an angle less than 45° relative to therotational axis. In FIG. 10, the feed direction 99 is parallel to therotational axis of the metal work piece. The first cutting edge 11 isactive and ahead of the nose cutting edge 10 in the feed direction 99.The first cutting edge is active, i.e. cuts metal, at an entering angleκ1, which is above 0°. The entering angle κ1 can be at least 5°. Forexample, the entering angle κ1 is in the range of 10-45°. In FIG. 10,the entering angle κ1 is around 5°. A larger entering angle κ1 shall bechosen if a larger depth of cut is needed.

The first cutting edge 11 is a leading edge. The second cutting edge 12is a trailing edge. The surface 53 is at least partly formed by the nosecutting edge 10. The surface 53, which is formed is a rotationalsymmetrical surface, i.e. a surface 53, which has an extension along therotation axis of the metal work piece and where in cross sectionsperpendicular to the rotational axis, each portion of the rotationalsymmetrical surface 53 is located at a constant distance from therotation axis of the metal work piece, where a constant distance is adistance which is within 0.10 mm, for example within 0.05 mm.

The rotational symmetrical surface 53 can be in the form of e.g. acylindrical surface or a conical surface or a frustoconical surface or atapered surface. The rational symmetrical surface 53 that is generatedor formed at least partly by the nose cutting edge 10 has a wavy shapewith small peaks and valleys, and the wavy shape is influenced at leastpartly by the curvature of the nose radius and the feed rate. The waveheight can be less than 0.10 mm, for example, less than 0.05 mm. Theactive nose cutting edge 10 is the part of the turning insert 1 and thepart of the turning tool 3 which is closest to the rotational axis ofthe metal work piece.

FIG. 11 shows the principle of conventional turning, where C1 representsthe feed direction in FIG. 1, and D1 represents the wear on or at a noseportion from such operation. C3 represents a conventional facingoperation, i.e. feed perpendicular and towards the rotational axis A3,and D3 represents the wear on or at a nose portion from such operation.The second cutting edge 12 is the main cutting edge in C1 feeddirection. The first cutting edge 11 is the main cutting edge in C3 feeddirection. A convex nose cutting edge 10 connects the first and secondcutting edges 11, 12. Transition points T1, T2 represent the transitionbetween the nose cutting edge 10 and the first 11 and second 12 cuttingedge, respectively. The wear D1, D3, is dependent on both the depth ofcut and the feed rate. However, it is clear that D1 and D3 overlap,resulting in high wear at the nose cutting edge 10, or at least at acenter portion of the nose cutting edge 10.

FIG. 12 shows the principle of an alternative turning method. C2represents the main feed direction in FIG. 2, or the main feed directionin pass 2, 4, 6 and 8 in FIG. 13, i.e. an axial feed direction away fromthe clamping end of the metal work piece. D2 represents the wear on orat a nose portion from such operation. C4 represents an out-facingoperation, i.e. feed perpendicular to and away from the rotational axisA3, as seen in the main feed directions in pass 1, 3, 5 and 7 in FIG.10. D4 represents the wear on or at a nose portion from such operation.The second cutting edge 12 is the main cutting edge in C4 feeddirection. The first cutting edge 11 is the main cutting edge in C2 feeddirection. A convex nose cutting edge 10 connects the first and secondcutting edges 11, 12. Transition points T1, T2 represent the transitionbetween the nose cutting edge 10 and the first 11 and second 12 cuttingedge, respectively.

Each wear D2, D4, is dependent on both the depth of cut and the feedrate. However, it is clear that D2 and D4 do not overlap, or at leastoverlap to a lesser degree than in FIG. 11, resulting in reduced wear atthe nose cutting edge 10, or at least reduced wear at a center portionof the nose cutting edge 10. The wear of the first and second cuttingedges 11, 12 has a wider range, i.e. is distributed over a longerdistance, compared to FIG. 11. However, because the smaller enteringangles in feed C2 and C4 compared to the greater entering angles in C1and C3, the chip thickness in FIG. 12 will be thinner and therefor giverelatively small wear. At constant feed rate and depth of cut, the areaof D2 is equal to the area of D3, and the area of D1 is equal to thearea of D4.

FIG. 13 show an example of a machining sequence using the first turninginsert. The left-hand side is the clamping end of the metal work piece.A 90° corner including a cylindrical surface 53 and a flat surface 56 isformed by turning. A sequence of steps 1-8 is shown. The entry for eachstep is shown as being perpendicular to the main feed direction of eachstep. The main feed direction in steps 1, 3, 5 and 7 is perpendicular toand away from the rotational axis A3. The main feed direction in steps2, 4, 6 and 8 is parallel to the rotational axis A3 and away from theclamping end. The entry for each cut is preferably as described inconnection to FIG. 2. The wear of the turning insert 1 after thesequence of steps showed in FIG. 13 is similar or identical to the wearshown in FIG. 12.

FIGS. 16a-17c further describe the first turning insert, as well as aturning tool 3 which includes the turning insert 1 and a tool body 2.The turning insert 1 includes a top surface 8, which is or includes arake face, and an opposite bottom surface 9, functioning as a seatingsurface. A reference plane RP is located parallel to and between the topsurface 8 and the bottom surface 9. A center axis A1 extendsperpendicular to the reference plane RP and intersects the referenceplane RP, the top surface 8 and the bottom surface 9. A hole, for ascrew, having openings in the top surface 8 and the bottom surface 9 isconcentric with the center axis A1. The turning insert 1 includes sidesurfaces 13, 13′, 13″, functioning as clearance surfaces, connecting thetop surface 8 and the bottom surface 9.

Three nose portions 15, 15′, 15″ are formed symmetrically relative to oraround the center axis A1. The nose portions 15, 15′, 15″ are identical.Each nose portion 15, 15′, 15″ includes a first cutting edge 11, asecond cutting edge 12 and a convex nose cutting edge 10 connecting thefirst 11 and second 12 cutting edges. The nose cutting edges 10, 10′,10″ are located at a largest distance from the center axis A1, i.e. at alarger distance from the center axis A1 than all other parts of theturning insert. In a top view, seen in FIG. 16d , the first 11 andsecond 12 cutting edges on or at the same nose portion 15 forms a noseangle α of 25-50° relative to each other, in FIG. 16d the nose angle αis 35°.

In a side view, such as in FIG. 16b , at least a portion of the firstand second cutting edges 11, 12 on or at each nose portion 15, 15′, 15″slopes towards the bottom surface, such that in a side view, the firstand second cutting edges 11, 12 have the highest points thereofbordering to the nose cutting edge 10 on or at the same nose portion 15.In other words, the distance from the first cutting edge 11 and thesecond cutting edge 12 to the reference plane RP varies in such a waythat that this distance is decreasing at an increasing distance from thenose cutting edge 10.

The first and second cutting edges 11, 12 are linear or straight, orsubstantially linear or straight in a top view. Bisectors 7, 7′, 7″extend equidistantly from each pair of first 11, 11′, 11″ and second 12,12′, 12″ cutting edges. Each bisector 7, 7′, 7″ intersects the centeraxis A1. Indentations 17, 17′, 17″ are formed between each pair of nosecutting edges 10, 10′, 10″.

The bottom surface 9, seen in FIGS. 18a and 18b , includes rotationprevention means, with the purpose of reducing the tendency for theturning insert 1 to rotate around the center axis A1 during cutting, inthe form of three grooves 40, 40′, 40″, each groove 40, 40′, 40″ havinga main extension in the same direction as the bisector 7, 7′, 7″ locatedadjacent the closest first 11 and second 12 cutting edges. Each groove40, 40′, 40″ includes two seating surfaces, for example, at an obtuseangle, 100-160°, in relation to each other.

The turning insert 1 is intended to be securely clamped, by clampingmeans such as a screw or a top clamp, in an insert seat 4 located at afront end of a tool body 2, as seen in FIG. 17a . The contact betweenthe insert seat 4 and the turning insert will now be described, see theshaded areas in FIG. 17c and FIG. 17a . The active nose cutting portion15 is the part of the insert where groove 40 is located in FIG. 17c .The two seating surfaces of groove 40 are in contact with two surfacesof a ridge 90 in the bottom of the insert seat 4. One surface of eachother groove 40′, 40″, the surfaces located at the largest distance fromthe active nose cutting edge 10, are in contact with bottom surfaces 93,94 in the bottom of the insert seat 4. At least portions of the sidesurface 13 located at the greatest distance from the active nose cuttingedge 10 may be in contact with rear seating surfaces 91, 92 formed at arear end of the insert seat 4.

FIGS. 14a-f show a second turning insert 1, as well as, a turning tool3, which includes the turning insert 1 and a tool body 2. The turninginsert 1 includes a top surface 8, which is or provides a rake face, andan opposite bottom surface 9, functioning as a seating surface. The top8 and bottom 9 surfaces are identical. This means that while in a firstposition, the top surface 8 functions as a rake surface, when the insertis turned upside down, the same surface is now functioning as a seatingsurface.

A reference plane RP is located parallel to and between the top surface8 and the bottom surface 9. A center axis A1 extends perpendicular tothe reference plane RP and intersects the reference plane RP, the topsurface 8 and the bottom surface 9. A hole for a screw, having openingsin the top surface 8 and the bottom surface 9 is concentric with thecenter axis A1.

The turning insert 1 includes side surfaces 13, 13′, 13″, functioning asclearance surfaces, connecting the top surface 8 and the bottom surface9. Three nose portions 15, 15′, 15″ are formed symmetrically relative toor around the center axis A1. The nose portions 15, 15′, 15″ areidentical. Each nose portion 15, 15′, 15″ includes a first cutting edge11, a second cutting edge 12 and a convex nose cutting edge 10connecting the first 11 and second 12 cutting edges. The nose cuttingedges 10, 10′, 10″ are located at a largest distance from the centeraxis A1, i.e. at a larger distance from the center axis A1 than allother parts of the turning insert.

In a top view, seen in FIG. 14d , the first 11 and second 12 cuttingedges on or at the same nose portion 15 form a nose angle α of 25-50°relative to each other, in this case 45°. In a side view, seen in FIG.14b , at least a portion of the first and second cutting edges 11, 12 onor at each nose portion 15, 15′, 15″ slopes towards the bottom surface,such that in a side view, the first and second cutting edges 11, 12 havethe highest points thereof adjacent to the nose cutting edge 10 on or atthe same nose portion 15. In other words, the distance from the firstcutting edge 11 and the second cutting edge 12 to the reference plane RPvaries in such a way that that this distance is decreasing as thedistance from the nose cutting edge 10 increases.

The first and second cutting edges 11, 12 are linear or straight, orsubstantially linear or straight in a top view. Bisectors 7, 7′, 7″extend equidistantly from each pair of first 11, 11′, 11″ and second 12,12′, 12″ cutting edges. Each bisector 7, 7′, 7″ intersects the centeraxis A1. Indentations 17, 17′, 17″ are formed between each pair ofadjacent nose cutting edges 10, 10′, 10″. The turning insert 1 includesrotation prevention means in the form of a set of surfaces 41, 42, 43,44, where each surface 41, 42, 43, 44 extends in a plane which forms anangle of 5-60° in relation to the reference plane RP. The set ofsurfaces 41, 42, 43, 44 are formed at a central ring-shaped protrusion30, extending around the center axis A1. By such a configuration, theturning insert 1 can be made double-sided or reversible, giving anincreased possible usage.

The first chip breaker wall 34 can be a part of the set of surfaces 41,42, 43, 44. An alternative solution (not shown) is to arrange the firstchip breaking wall 34 as part of a further protrusion (not shown) at agreater distance from the center axis A1. FIG. 14e show one possibleclamping mode of the turning insert 1 by means of a clamp 95, whichpresses the insert and keeps the insert in the insert seat 4 of the toolbody 2.

FIG. 14f shows the insert seat 4 in which the second turning insert 1can be mounted by means of e.g. a top clamp 95. The side surface 13located at a greatest distance from the active nose cutting edge 10includes two surfaces, which are pressed against rear surfaces 91, 92 ofthe insert seat 4. The set of surfaces 41, 42, 43, 44 includes two frontsurfaces 41, 42, which are in contact with surfaces of a front portion90 of the bottom of the insert seat 4. Front in this context is betweenthe center axis A1 and the active nose cutting edge 10. The set ofsurfaces 41, 42, 43, 44 further includes two rear surfaces 43, 44, whichare pressed against rear bottom surfaces 93, 94 which are located in thebottom surface of the insert seat 4, between the front portion 90 andthe rear surfaces 91, 92 of the insert seat 4.

Reference is made to FIG. 2a , which shows turning using a third turninginsert. As in FIG. 1, a metal work piece is clamped by clamping jaws(not shown), which are pressed against an external surface at a firstend 54, or clamping end, of the metal work piece. An opposite second end55 of the metal work piece is a free end. The metal work piece rotatesaround a rotational axis A3. The turning insert, seen in top view, issecurely and removably clamped in an insert seat or a pocket in toolbody 2 by means of a screw. The tool body 2 has a longitudinal axis A2,extending from a rear end to a front end, in which the insert seat orpocket is located. In FIG. 2a , the feed is, to a greatest extent,axial, also called longitudinal feed, i.e. the direction of the feed isparallel to the rotational axis A3. In this way, an external cylindricalsurface 53 is formed. At the entry of each cut, or immediately prior tothe axial feed, the feed has a radial component, in such a way that theturning insert move along an arc of a circle.

The turning insert includes two opposite and identical nose portions 15,15′ formed 180° relative each other around a center axis of the turninginsert 1. Each nose portion 15, 15′ includes a first cutting edge 11, asecond cutting edge 12 and a convex nose cutting edge 10 connecting thefirst 11 and second 12 cutting edges. One nose portion 15, locatedcloser to the rotational axis A3 than the opposite inactive nose portion15′, is active. Active means that the nose portion as placed such thatit can be used for cutting chips from the metal work piece 50. Abisector 7 extending equidistantly from the first 11 and second 12cutting edges, intersecting the center of the nose cutting edge 10 and acenter axis A1 of the turning insert. The first and second cutting edges11, 12 converge at a point (not shown) outside the turning insert. Thebisector of the active nose portion 15 forms an angle θ, 40-50°,relative to the longitudinal axis A2.

In a top view the first 11 and second 12 cutting edges on the same noseportion 15 form a nose angle α of 70-85° relative to each other, whichin FIG. 2a is 80°. A third convex cutting edge 60 is formed adjacent tothe first cutting edge 11. A fourth cutting edge 61 is formed adjacentto the third cutting edge 60, further away from the nose cutting edge10. A fifth convex cutting edge 62 is formed adjacent to the secondcutting edge 12. A sixth cutting edge 63 is formed adjacent to the fifthcutting edge 62, further away from the nose cutting edge 10.

In top view, as in FIG. 2a , the first, second, fourth and sixth cuttingedges 11, 12, 61, 63 are linear or straight, or substantially linear orstraight. The main feed direction, towards the right in FIG. 2a , isparallel to the rotational axis A3 and away from the first end 54, orclamping end, of the metal work piece 50. In the feed direction, thefourth cutting edge 61 is active at an entering angle κ1 of 10-45°, forexample, 20-40°, which in FIG. 2a is 30°. The fourth cutting edge 63 isthe main cutting edge in the feed direction, i.e. the majority of thechips are cut by the fourth cutting edge 63, at least at moderate tohigh depth of cut. To a lesser degree, third cutting edge 60, the firstcutting edge 11 and the nose cutting edge 10 are also active. The firstcutting edge is ahead of the nose cutting edge 10 in the axial feeddirection. All parts of the turning insert is ahead of the active nosecutting edge 10 in the feed direction. The second cutting edge 11,formed on the active nose portion 15, is inactive.

In the axial turning operation, chips can be directed away from themetal work piece in a trouble-free manner, especially compared to themachining shown in FIG. 1 where the feed is towards the clamping end andtowards a wall surface. In the machining step in FIG. 2a , the turninginsert 1 enters into the metal work piece 50 such that the nose cuttingedge 10 moves along an arc of a circle. The turning insert 1 enters intothe metal work piece 50, or goes into cut, such that the chip thicknessduring entry is constant or substantially constant. At the entry, thedepth of cut is increased from zero depth of cut. Such preferred entryreduces the insert wear, especially the wear at the nose cutting edge10. Chip thickness is defined as feed rate multiplied by entering angle.Thus, by choosing and/or varying the feed rate and the movement and/ordirection of the turning insert during entry, the chip thickness can beconstant or substantially constant. The feed rate during entry can beless or equal than 0.50 mm/revolution. The chip thickness during entryis less than or equal to the chip thickness during subsequent cutting ormachining.

If the feed direction would be radial, in such a way that the feeddirection would be perpendicular to and away from the rotational axisA3, the sixth cutting edge 63 would be active at an entering angle κ2 of10-45°, for example, 20-40°.

The cylindrical surface 53, or rational symmetrical surface, generatedor formed at least partly by the nose cutting edge in FIGS. 1 and 2 a,has a wavy shape with small peaks and valleys, and the wavy shape isinfluenced at least partly by the curvature of the nose radius and thefeed rate. The wave height is less than 0.10 mm, for example, less than0.05 mm. A thread profile is not a cylindrical surface 53 in this sense.

In FIG. 3a , the turning insert and tool body in FIG. 2a can be seen inalternative machining operations, showing the versatile application areaof the turning tool, especially with regard to feed direction. Amachining sequence in six steps is shown. Step 1 is a undercuttingoperation. Step 2 is axial turning away from the first end 54, orclamping end, of the metal work piece. Step 3 is a profiling operationin the form of a feed which has both an axial and a radial component,generating a conical or frustoconical surface. Step 4 is an operationsimilar to step 2. Step 5 is an out-facing operation generation a flatsurface located in a plane perpendicular to the rotational axis A3 ofthe metal work piece. Step 6 is an out-facing operation at the secondend 55, or free end, of the metal work piece.

FIGS. 15a-f and FIGS. 17d-f further describe the third turning insert 1,as well as a turning tool 3, which includes the turning insert 1 and atool body 2. The turning insert 1 includes a top surface 8, which is orincludes a rake face 14, and an opposite bottom surface 9, functioningas a seating surface. A reference plane RP is located parallel to andbetween the top surface 8 and the bottom surface 9. A center axis A1extends perpendicular to the reference plane RP and intersects thereference plane RP, the top surface 8 and the bottom surface 9. A screwhole having openings in the top surface 8 and the bottom surface 9 isconcentric with the center axis A1.

The third turning insert 1 includes side surfaces 13, functioning asclearance surfaces, connecting the top surface 8 and the bottom surface9. Two opposite nose portions 15, 15′ are formed symmetrically relativeto or around the center axis A1. The nose portions 15, 15′ areidentical. Each nose portion 15, 15′ includes a first cutting edge 11, asecond cutting edge 12 and a convex nose cutting edge 10 connecting thefirst 11 and second 12 cutting edges. Each nose portion 15, 15′ furtherincludes a third convex cutting edge 60, formed adjacent to the firstcutting edge 11, and a fourth cutting edge 61 formed adjacent to thethird cutting edge 60, further away from the nose cutting edge 10. Eachnose portion 15, 15′ further includes a fifth convex cutting edge 62formed adjacent to the second cutting edge 12, and a sixth cutting edge63 formed adjacent to the fifth cutting edge 62, further away from thenose cutting edge 10. In top view, as in FIG. 15d , the first, second,fourth and sixth cutting edges 11, 12, 61, 63 are linear or straight, orsubstantially linear or straight.

The nose cutting edges 10, 10′ are located at a largest distance fromthe center axis A1, i.e. at a larger distance from the center axis A1than all other parts of the turning insert. In a top view, seen in FIG.15d , the first 11 and second 12 cutting edges on the same nose portion15 forms a nose angle α of 75-85° relative to each other, in FIG. 15dthe nose angle α is 80°. In a side view, such as in FIG. 15c , at leasta portion of the fourth and sixth cutting edges 61, 63 on each noseportion 15, 15′, 15″ slopes towards the bottom surface 9, such that in aside view, the fourth and sixth cutting edges 61, 63 has the highestpoints thereof closer to the nose cutting edge 10 on the same noseportion 15. In other words, the distance from the fourth cutting edge 61and the sixth cutting edge 63 to the reference plane RP varies in such away that that this distance is decreasing at increasing distance fromthe nose cutting edge 10. Further, the first, second third and fifthcutting edges 11, 12, 60, 62 are sloping towards the bottom surface 9 ina corresponding manner, such that in relation to the bottom surface 9,the nose cutting edge 10 is further away than the first and secondcutting edges 11, 12, which in turn are further away than the third andfifth cutting edges 60, 62, which in turn are further away than thefourth and sixth cutting edges 61, 63.

Bisectors 7, 7′ extend equidistantly from each pair of first 11, 11′ andsecond 12, 12′ cutting edges. Each bisector 7, 7′ intersects the centeraxis A1, and the bisectors 7, 7′ extend in a common direction. Thebottom surface 9 is identical to the top surface 8. In a top view, as inFIG. 15d , the fourth cutting edge 61 forms an angle β of 0-34° relativeto the bisector 7, which in FIG. 15d is 10-20°.

The top surface 8 includes protrusions 30 having a first chip breakerwall 34 facing the fourth cutting edge 61. The distance from the fourthcutting edge 61 to the first chip breaker wall 34 is increasing awayfrom the nose cutting edge 10. The protrusions 30 are intended tofunction as seating surfaces, and the top surface of each protrusion isflat and parallel to the reference plane RP. The protrusions 30 are thepart of the turning insert 1 which are located at the greatest distancefrom the reference plane RP. The protrusion includes a second chipbreaker wall facing the sixth cutting edge. The distance, from thefourth cutting edge 61 to the first chip breaker wall 34, is measured ina direction perpendicular to the fourth cutting edge 61, and in a planeparallel to the reference plane RP, to the first chip breaker wall 34.The protrusion 30, and thus the first chip breaker wall 34, does notnecessarily have to extend along the whole length of the fourth cuttingedge 61. Still, the distance from the fourth cutting edge 61 to thefirst chip breaker wall 34 is increasing at the portion of the fourthcutting edge 61 where perpendicular to this fourth cutting edge 61, thefirst chip breaker wall 34 extends.

A distance D1 measured in a plane perpendicular to the reference planeRP between the top surface of the protrusion 30 and the lowest point ofthe fourth cutting edge 61 is 0.28-0.35 mm. Bumps 80, or protrusions,are formed in the top surface 8. The bumps 80 are located at a distance,greater than 0.3 mm and less than 3.0 mm, from the fourth cutting edge61. The bumps 80 are located between the fourth cutting edge 61 and thefirst chip breaker wall 34. The bumps 80 have a non-circular shape intop view, such that a major extension, which is 0.8-3.0 mm, of the bumpsis in a direction substantially perpendicular to or perpendicular to thefourth cutting edge 61. The minor extension of the bumps perpendicularto the major extension is 0.5-2.0 mm. The bumps 80, or protrusions, areportions of the top surface 8 which extends away from the referenceplane in relation to the surrounding area.

In a top view as in FIG. 15d , the bumps 80 can have an elliptic or ovalor substantially elliptic or oval shape. The bumps 80 are separated fromeach other. The bumps 80 can be located at a constant distance from eachother. The bumps 80 also can be located at a constant distance from thefourth cutting edge 61. In the first embodiment, there are 5 bumpsadjacent to the fourth cutting edge. It is possible to have 2-10 bumpsadjacent to the fourth cutting edge.

There is at least one further bump 80, for the third turning insertthere are 2-3 bumps 80, located perpendicular to and having an majorextension in a direction perpendicular to the third cutting edge 60, andat least one further bump 80, in the first embodiment 1-2 bumps 80,located perpendicular to and having an major extension in a directionperpendicular to the first cutting edge 11.

The third turning insert 1 is symmetrical, or mirror images, on oppositesides of the bisectors 7, 7′. Therefore, bumps 80 are formed in acorresponding manner at a distance from the second, fifth and sixthcutting edges 12, 62, 63.

By such a turning insert 1, chip breaking and/or chip control is furtherimproved, especially at lower depth of cut, i.e. when the depths of cutis such that the first cutting edge 11 is active and that the fourthcutting edge 61 is inactive. At such low depth of cut, the chip is verythin, due to the low entering angle by the first cutting edge 11, andthe bump or bumps 80, closest to the first cutting edge 11, function aschip breakers. The major extension of the bumps 80 gives the effect thatthe time, until the wear of the bumps 80 reduces the effect of the bumps80 on the chips, is increased.

Reference is now made to FIGS. 18-22 a-e, which shows a fourth, fifth,sixth, seventh and eighth type of turning insert, respectively, suitablefor the method according to the invention. These inserts differ from thethird insert only with regards to the bottom surface and the sidesurfaces.

Thus, the fourth, fifth, sixth, seventh and eighth turning inserts 1,shown in FIGS. 18-22 a-e respectively, have the same or identical shape,form, dimension, value and interrelations between features and elementsas the third turning insert with regards to the top surface 8, referenceplane RP, screw hole, first cutting edge 11, nose cutting edge 10,second cutting edge 12, third cutting edge 60, fourth cutting edge 61,fifth cutting edge 62, sixth cutting edge 63, nose angle α, bisector 7,angle β, rake face 14, protrusion 30, first chip breaker wall 34, secondchip breaker wall, distance D1 and bumps 80.

The fourth, fifth, sixth and seventh turning inserts 1, shown in FIGS.18-21 a-e, are formed such that a first side surface 13 includes a firstclearance surface 21 adjacent to the first cutting edge 11, a thirdclearance surface 23, and a second clearance surface 22 located betweenthe first clearance surface 21 and the third clearance surface 23.

The angle which the second clearance surface 22 forms in relation to thebottom surface 9, measured in a plane perpendicular to the first cuttingedge 11, is greater than the angle which the third clearance surface 23forms in relation to the bottom surface measured in a planeperpendicular to the first cutting edge 11.

The angle which the second clearance surface 22 forms in relation to thebottom surface 9, measured in a plane perpendicular to the first cuttingedge 11, is greater than the angle which the first clearance surface 21forms in relation to the bottom surface measured in a planeperpendicular to the first cutting edge 11.

The side surfaces 13, 13′ of each nose portion 15, 15′ are configuredsymmetrically in relation to a plane perpendicular to the referenceplane RP and comprising the bisector 7. The clearance surface adjacentto the second cutting edge 12 is formed or arranged in a correspondingmanner. The advantages from the clearance surface arrangements are thatout-facing can be performed at small metal work piece diameters, andthat larger depth of cut is possible in out-facing.

Reference is now made to FIGS. 18a-e , which shows the fourth turninginsert 1. The bottom surface 9 includes rotation prevention means 40, inorder to reduce movement of the turning insert 1 relative to the insertseat 4 during machining. The rotation prevention means 40 are in theform of two grooves 40, 40′ having a common major extension, which majorextension is corresponding to the extension of the bisectors 7, 7′.

Reference is now made to FIGS. 19a-e , which shows the fifth turninginsert 1. The bottom surface 9 includes rotation prevention means 40, inorder to reduce movement of the turning insert 1 relative to the insertseat 4 during machining. The rotation prevention means 40 are in theform of two grooves 40, 40′ having a common major extension, which majorextension is corresponding to the extension of the bisectors 7, 7′. Eachgroove 40, 40′ includes two surfaces which are form an obtuse angle, inthe range of 100-160°, in relation to each other.

Reference is now made to FIGS. 20a-e , which show a sixth turning insert1. The bottom surface 9 includes rotation prevention means 40, in orderto reduce movement of the turning insert 1 relative to the insert seat 4during machining. The rotation prevention means 40 are in the form oftwo ridges 40, 40′ having a common major extension, which majorextension is corresponding to the extension of the bisectors 7, 7′.

Reference is now made to FIGS. 21a-e , which show a seventh turninginsert. The bottom surface 9 includes a flat surface 9, which isparallel to the reference plane RP.

Reference is now made to FIGS. 22a-e , which show an eighth turninginsert 1. The bottom surface 9 includes a flat surface 9, which isparallel to the reference plane RP. The flat surface 9 is ring-shapedaround the center axis of the turning insert. A first side surface 13includes a first clearance surface 21 adjacent to the first cutting edge11 and a third clearance surface 23. The third clearance surface 23borders to the bottom surface 9.

The angle, which the first clearance surface 21 forms in relation to thebottom surface 9, measured in a plane perpendicular to the first cuttingedge 11, is greater than the angle which the third clearance surface 23forms in relation to the bottom surface measured in a planeperpendicular to the first cutting edge 11. The clearance surfaceadjacent to the second cutting edge 12 is formed or arranged in acorresponding manner. The advantages from the clearance surfacearrangements are that out-facing can be performed at small metal workpiece diameters, and that larger depth of cut is possible in out-facing.

The protrusion 30 includes grooves formed in the top surface of theprotrusion 30. The grooves have a major extension perpendicular to thebisector 7.

Although the present embodiment(s) has been described in relation toparticular aspects thereof, many other variations and modifications andother uses will become apparent to those skilled in the art. It ispreferred therefore, that the present embodiment(s) be limited not bythe specific disclosure herein, but only by the appended claims.

The invention claimed is:
 1. A method to form a surface on a metal workpiece comprising: a first machining step of providing a turning insertincluding a first cutting edge, a second cutting edge and a convex nosecutting edge connecting the first and second cutting edges, selecting anose angle formed between the first and second cutting edges to be lessthan or equal to 85°; arranging the orientation of the second cuttingedge such that it forms a back clearance angle of more than 90° in afeed direction; positioning all parts of the turning insert ahead of thenose cutting edge in the feed direction; rotating the metal work piecearound a rotational axis in a first direction; and moving the turninginsert in a direction parallel to or at an angle less than 45° relativeto the rotational axis such that the first cutting edge is active andahead of the nose cutting edge in the feed direction and such that thesurface at least partly is formed by the nose cutting edge.
 2. Themethod according to claim 1, wherein the first machining step furthercomprises the steps of clamping the metal work piece at a first end,setting the nose cutting edge a shorter distance to the first end thanall other parts of the turning insert and moving the turning insert in adirection away from the first end.
 3. The method according to claim 1,wherein the first machining step further comprises the step of arrangingthe first cutting edge such that the first cutting edge cuts metal chipsfrom the metal work piece at an entering angle κ1 of 10-45°.
 4. Themethod according to claim 1, wherein the turning insert includes a thirdconvex cutting edge adjacent to the first cutting edge and a fourthcutting edge adjacent to the third cutting edge, the method furthercomprising the step of arranging the fourth cutting edge such that thefourth cutting edge cuts metal chips from the metal work piece at anentering angle κ1 of 10-45°.
 5. The method according to claim 1, whereinthe first machining step further comprises the step of entering theturning insert into the metal work piece at an angle relative to therotation axis which is less than 90°, the angle being greater than theangle formed between the feed direction of the turning insert and therotation axis.
 6. The method according to claim 1, wherein the firstmachining step further comprises the step of entering the turning insertinto the metal work piece such that the nose cutting edge moves along anarc of a circle.
 7. The method according to claim 1, wherein the firstmachining step further comprises the step entering the turning insertinto the metal work piece such that the chip thickness during entry isconstant or substantially constant.
 8. The method according to claim 1,wherein the surface is an external cylindrical surface, and in that themoving of the turning insert is in a direction parallel to therotational axis.
 9. The method according to claim 1, wherein the turninginsert includes a top surface, an opposite bottom surface, and areference plane is located parallel to and between the top surface andthe bottom surface, the method further comprising the step of arrangingthe first cutting edge such that the distance from the first cuttingedge to the reference plane decreases as a distance from the nosecutting edge increases.
 10. The method according to claim 4, wherein theturning insert includes a top surface, an opposite bottom surface, and areference plane is located parallel to and between the top surface andthe bottom surface, the method further comprising the step of arrangingthe fourth cutting edge such that the distance the fourth cutting edgeto the reference plane decreases as a distance from the nose cuttingedge increases.
 11. The method according to claim 1, further comprisingthe step of setting the back clearance angle constant in relation to thefeed direction during the formation of the surface.
 12. The methodaccording to claim 1, further comprising the step of providing a turningtool including the turning insert and a tool body, wherein the methodcomprises the further step of positioning all parts of the tool bodyahead of the nose cutting edge in the feed direction.
 13. The methodaccording to claim 1, further comprising the step of providing a turningtool including the turning insert and a tool body, the tool body havinga front end and a rear end a main extension along a longitudinal axisextending from the front end to the rear end, an insert seat formed inthe front end in which the turning insert is mountable, and the step ofsetting the longitudinal axis of the tool body at an angle greater thanzero but less than or equal to 90° relative to the rotational axis ofthe metal work piece.
 14. The method according to claim 1, furthercomprising a second machining step of moving the turning insert in adirection away from the rotation axis such that the second cutting edgecuts chips from the metal work piece, and such that a surfaceperpendicular to the rotational axis of the metal work piece is formed.15. The method according to claim 14, further comprising the step of ina sequence alternating the first and second machining steps, such that acorner comprising two surfaces is formed.
 16. The method according toclaim 14, further comprising the step of in a sequence alternating thefirst and second machining steps, such that an external 90° cornerincluding two wall surfaces is formed, wherein one wall surface is anouter cylindrical surface and another wall surface is perpendicular tothe rotational axis of the metal work piece.
 17. The method according toclaim 1, the method further comprising a third machining step,comprising the steps of rotating the metal work piece around therotation axis in a second direction, in that the second direction ofrotation is opposite to the first direction of rotation, and moving theturning insert in a direction towards the rotation axis such that thesecond cutting edge cuts chips from the metal work piece.
 18. The methodaccording to claim 1, comprising the step of providing a turning toolincluding the turning insert and a tool body the tool body having afront end and a rear end, a main extension along a longitudinal axisextending from the front end to the rear end, an insert seat formed inthe front end in which the turning insert is mountable such that abisector extending equidistantly from the first and second cutting edgesforms an angle θ of 35-55° in relation to the longitudinal axis of thetool body.
 19. The method according to claim 18, comprising the step ofarranging the first cutting edge a shorter distance from thelongitudinal axis of the tool body than the distance from the secondcutting edge to the longitudinal axis of the tool body.
 20. A computerprogram having computer executable code, which when executed by acomputer numerical control lathe cause the computer numerical controllathe to perform the method according to claim
 1. 21. A computerreadable medium having stored thereon a computer program according toclaim
 20. 22. A data stream which is representative of a computerprogram according to claim 20.